Light fixtures creating various effects are getting more and more used in the entertainment industry in order to create various light effects and mood lighting in connection with concerts, live shows, TV shows, sport events or as a part on architectural installation. Entertainment light fixtures creates typically light beam having a beam width and a divergence and can for instance be wash/flood fixtures creating a relatively wide light beam with a uniform light distribution or it can be profile fixtures adapted to project image onto a target surface.
Light emitting diodes (LED) are, due to their relatively low energy consumption or high efficiency, long lifetime, and capability of electronic dimming, becoming more and more used in connection with lighting applications. LEDs are used in lighting applications for general illumination such as wash/flood lights illuminating a wide area or for generating wide light beams e.g. for the entertainment industry and/or architectural installations. For instance like in products like MAC101™, MAC301™, MAC401™, Stagebar2™, Easypix™, Extube™, Tripix™, Exterior 400™ series provided by the applicant, Martin Professional a/s. Further LEDs are also being integrated into projecting systems where an image is created and projected towards a target surface. For instance like in the product MAC 350 Entrour™ provided by the applicant, Martin Professional A/S.
The light in projecting systems is generally collected into an optical gate where the image is generated, and an imaging optical system projects the gate onto a target surface. WO0198706, U.S. Pat. No. 6,227,669 and U.S. Pat. No. 6,402,347 disclose lighting systems comprising a number of LEDs arranged in a plane array where a converging lens is positioned in front of the LED in order to focus the light, for instance to illuminate a predetermined area/gate or for coupling the light from the diodes into an optical fiber.
U.S. Pat. No. 5,309,277, U.S. Pat. No. 6,227,669, WO0198706, JP2006269182 A2, EP1710493 A2, U.S. Pat. No. 6,443,594 disclose lighting systems where the light from a number of LEDs is directed towards a common focal point or focusing area, for instance by tilting the LEDs in relation to the optical axis (JP2006269182 A2, WO0198706, U.S. Pat. No. 5,309,277) or by using individually refracting means positioned in front of each LED (U.S. Pat. No. 6,443,594, U.S. Pat. No. 7,226,185B, EP1710493).
WO06023180 discloses a projecting system comprising a LED array with a multiple number of LEDs where the light from the LEDs is directed towards a target area.
The prior art fixtures try to increase the lumen output by adding as many light sources as possible. The consequence is, however, that the efficiency with regard to power consumption versus light output is very low, as it is fundamentally only possible to effectively utilize light sources of same or less Etendue as the imaging optics in this kind of optical system. So if the source Etendue is a close match to the Etendue of the imaging system there are no gains in using multiple sources in order to increase the light output (intensity/lumen) as the Etendue of the light sources then will be larger than the Etendue of the imaging system and the imaging system is thus not capable of collecting the light
Furthermore, a large amount of light is lost as the prior art fixtures typically only couple a central part of the light of the light beams through the gate in order to provide a uniform illumination of the gate, which again reduces the efficiency. The space in light fixtures is often limited and it is difficult to fit many light sources into prior art fixtures, for instance because the optical components associated with the light sources often take up a lot of space. Yet another aspect is the fact that color artifacts often appear in the output from fixtures having light sources of different colors. The reason for this is the fact that high performance LEDs used for stage-illumination have large, rectangular die areas of 1-12 mm2 and even higher This implies, that it is not possible to model the primary optics to a point source since the size-ratio between the primary optics and the LED die can get rather small. Furthermore, the rectangular shape can also be imaged in the output as rectangular patches. Compared to discharge lamps, these patches are ill fitted to smoothly fill out the circular spot profiles of stage-illumination instruments.